Combining lenses: Sigma 150mm 2.8, Xenoplan 28mm 2.0

dickb · Post by **dickb** » Thu Oct 25, 2018 12:03 pm

Inspired by Robert's good results with a combination of Sony A6300, Sigma OS 150/2.8 and Xenon 28/2.0 I did a quick and literally dirty test of my vaguely comparable equipment. I used a Canon 5D mkII, a Sigma 150/2.8 (non-OS version) (at f/2.

and a reverse mounted Schneider Xenoplan 28/2.0 (at f/2.0). The Sigma is focussed close to its minimum focus distance in order to eliminate the worst vignetting. Lighting with a single Jansjo LED lamp. The resulting magnification is roughly 12:1.

Preliminary conclusions:

- I need to clean my disc
- this isn't the best combination of lenses for a full frame camera, a longer focal length tube lens may be better
- this is a very promising result
- I will need a lot of dark winter nights testing the many permutations of lens combinations

whole full frame image:

centre crop

JohnyM · Post by **JohnyM** » Thu Oct 25, 2018 12:20 pm

Try with sigma @infinity?

dickb · Post by **dickb** » Thu Oct 25, 2018 1:03 pm

JohnyM wrote:Try with sigma @infinity?

Here you go, an equally quick and dirty sample of the same combination but with the Sigma at infinity. More vignetting and field curvature, but it may work well with an APS-C camera. Magnification is now around 10:1.

1:1

I don't claim that this is the best this combination can be even - maybe using a shorter stack of stepping rings may get better results, there may be several variables to tweak. I was just surprised to see how decent a result I got at first try.

Lou Jost · Post by **Lou Jost** » Thu Oct 25, 2018 1:32 pm

Good result. I bet you could stop it down very slightly with a paper Waterhouse stop between the lenses to improve it.

elimoss · Post by **elimoss** » Sat Oct 27, 2018 12:41 pm

Xenoplans have a small image circle; not even designed for APS-C coverage (at regular distances, of course)

dickb · Post by **dickb** » Sat Oct 27, 2018 1:44 pm

elimoss wrote:Xenoplans have a small image circle; not even designed for APS-C coverage (at regular distances, of course)

Indeed. But there is a considerable difference between various Xenoplans and Apo Xenoplans. Most are designed for very small image circles, some have relatively large ones, specifically those labelled as anti-shading. The 28/2.0 has a relatively large image circle, this is an image taken with my Sony A7 full frame camera:

elimoss · Post by **elimoss** » Sat Oct 27, 2018 2:34 pm

Neat. So I guess it is designed for low or no vignetting (shading) on whatever C mount industrial devices it is typically used on.

Pretty impressive, actually, because it's tiny!

dickb · Post by **dickb** » Wed Nov 28, 2018 3:22 pm

Another quick and very dirty test to get a good image from the Xenoplan 28/2.0. This time I used my Canon 5DmkII, Canon 70-200/2.8 IS II, Canon extender 2x III at 400mm at f/7.1 with the Xenoplan at f/4.0

The lighting were 2 diffused Jansjo Led lights.

The width of the subject is just under 3 mm, resulting in just over 12:1 magnification:

1:1

This is just an indication, there are many aspects that may well be improved, from focus perfection and subject perpendicularity to lighting angle, reversed lens to front lens distance and additional Waterhouse stop.